Completely Automated Public Turing Test to tell Computers and Humans Apart (CAPTCHA) is used as a guard from malicious script like bots. This method is mainly used to differentiate the user accessing website is a valid user or not. The present research deals with image based techniques that incorporate object identification as an initial authentication to provide solution. This method is simple for humans to solve and provides high level of security by being resilient to computerized attacks. The required objects for this method to create a captcha are stored in a database. A composite image is generated randomly by combining at least four images and a single question is related to it. For each displayed image, appropriate questions are generated and stored in the database. User has to choose appropriate picture based on the question which appears on the screen. Text will be embedded into the image. User should pick the appropriate text and the respective text will be activated in the chosen area. Arithmetic operation is solved using random values. Then system will verify the text and generate response based on the selection. If the user clicked-image is correct, and then the user is considered as a valid user, otherwise the user is considered as a robot or computerized script. Keywords: Captcha, Security, Secured Transaction, Online Security, Turing test.
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